Distilling a lubricating oil with an aldehyde and a solid reagent to produce color stable lubricating oil fractions



United States Patent DISTILLING A LUBRICATIN G OIL WITH AN ALDE- HYDE AND A SOLID REAGENT TO PRODUCE COLOR STABLE LUBRICATING OIL FRACTIONS Chester E. Wilson, Anaheim, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application December 22, 1953, Serial No. 399,827

13 Claims. (Cl. 196-35) This invention relates to the treatment of hydrocarbon oils, especially hydrocarbon oils falling in the lubricating oil viscosity range, to produce relatively color stable products. More particularly, the invention relates to the product of color stable distillate oils of lubricating oil viscosity obtained by treating crude oils, reduced crude oils, lubricating distillates and solvent extracts from lubricating oil distillate-s, prior to and/ or during distillation, with an aldehyde and a catalyst which may be an alkali or a clay.

The production of color stable lubricating oils or lubricating oil fractions of petroleum by treatment with selective solvents, with sulfuric acid and/or activated clays is well known. Such procedures which result in the production of relatively stable products, however, are costly and wasteful. Thus in preparing high quality lubricating oils by sulfuric acid treatment, followed with clay treatment, there are appreciable losses of material in the acid sludge, as well as in hold up on the clay. Also treatment of lubricating oil distillates and the like with a selective solvent results in the production of appreciable quantities of extract material which is not suitable for use in lubricating oils. Moreover, treatment of some distillates with economic proportions of activated clay does not yield the desired color stable products.

There is need in the industry for distillate oils which are reasonably color stable but which may contain or even will desirably contain appreciable quantities of the more aromatic or naphthenic portions of the oil, which material would be lost by treatment with selective solvents or with sulfuric acid. Thus, there is a need for a relatively cheap oil in the lubricating oil viscosity range, but such oils will desirably be color stable. Oils of this character have utility in many applications Where oxidation stability and the like, is not required. Such uses include use in crankcases of older automotive engines, use in various kinds of machinery, as for example farm machinery, use in preparing lost cost greases, as for example cup greases and sett greases, use as processing or plasticizing oils, as for example in some rubber processing operations.

it has been found that by adding a small amount of formaldehyde, formaldehyde genitor or other relatively low molecular weight aldehyde, as for example acetaldehyde, propionaldehyde, furfuraldchyde and the like, together with a base, as for example sodium hydroxide, or a clay as for example bentonite, to a crude oil, reduced crude oil, a lubricating oil fraction or a lubricating oil extract fraction, and heating and mixing, followed by distillation of the mixture, distillate fractions are obtained which are relatively far more color stable than fractions obtained by simple distillation of such mineral oils.

it is an object of this invention to produce distillate fractions of lubricating oil grade from crude oil, reduced crude oil, mineral oil distillates or from lubricating oil extracts, which distillate fractions have good color stabil'ity.

Another object of the invention is to produce low cost 2 lubricating oils in high yield, which lubricating oil fractions have good color stability.

A further, object of the invention is to provide a method of producing color stable petroleum fractions in the lubrieating oil viscosity range by a simple method involving treating a crude oil, reduced crude oil or a lubricating oil extract fraction and/or distilling such materials with a small amount of aldehyde or aldehyde genitor, together with an auxiliary agent, as for example an alkali or alkaline earth metal base or an activated clay.

In carrying out the process of this invention, a crude oil, reduced crude oil, lubricating oil distillate fraction or lubricating oil extract fraction is mixed with from 0.1% to 2% by weight of a low molecular weight aldehyde or an aldehyde genitor and between 0.02% and about 0.5% by weight of sodium hydroxide or other alkali or alkaline earth metal hydroxide or an active clay, and the mixture fractionally distilled to recover as overhead, lubricating oil fractions. The resulting overhead fractions are found to have a color substantially the same as overhead fractions obtained by distilling in the absence of aldehyde and base, or clay, but on standing for a period of a few weeks, the color degradation of the fractions obtained by the process of this invention is far less than that observed in the case of simple distillates. Thus, although there is generally little or no improvement in the initial color, the lubricating oil distillates produced in a distillation in the presence of aldehyde and base, or clay, are relatively color stable.

As an illustration, a sample of a topped, California heavy crude was vacuum distilled in the presence of approximately 1.3% by weight of 37% formalin and approximately 0.06% by weight of sodium hydroxide added in the form of a 50% aqueous solution. The initial color of the lubricating oil distillate was 3+ A. S. T. M. After storage for ten weeks in the dark but in the presence of air, the color was 5 A. S. T. M. For comparison, a sample of the same topped crude was distilled without aldehyde and caustic and the lubricating oil distillate also had an original color of 3+ A. S. T. M., however, the color was 7 A. S. T. M. after six weeks, darker than 8 after seven weeks, and at ten weeks the color was dark.

Inorder to show the effect of the use of aldehyde in the absence of caustic, a third portion of the same topped California crude was distilled in the presence of 1.3% by weight of formalin without the use of caustic. The lubricating oil fraction recovered had an initial color of 3+ A. S. T. M. and after ten weeks storage the color was 6 A. S. T. M. Furthermore, a lubricating oil distillate obtained from the same topped crude by distilling in the presence of 0.06% by weight of sodium hydroxide without the use of formalin had an initial color of 3 A. S. T. M. and after storage for eight weeks had a color of 8 A. S. T. M. The improvement in color stability of distillates obtained by treatment with the aldehyde and base, or clay, is observed in the case of many crude oils and fractions thereof, although the treatment is usually applied to the naphthenic type crude oils, such as the California and gulf coast crude oils, and other crudes from which lubricating oils of low wax content may be produced directly. Also, the same improvement is noted in distillate fractions obtained by distilling lubricating oil extract fractions produced as a by-product in the manufacture of solvent-treated mineral lubricating oils. The distillate fractions from lubricating oil extracts obtained by the process of this invention have particular value as oils for rubber processing, for use in the preparation of plastic tile and the like where oils of low aniline point have particular utility.

Aldehydes which may be used include formaldehyde, acetaldehyde, propionaldehyde and furfuraldehyde, as well as' the aldehyde genitors, as for example paraformaldehyde, trioxane and the like. Furthermore, in addition to sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide may be used as the auxiliary or catalytic agent. These will all be used in the amounts indicated hereinabove.

It is found also that clays of the character employed for clay treatment of lubricating oil fractions and the like, and particularly the so-called activated treating clays, may be used in place of the alkali or alkaline earth metal hydroxides. Where clay is employed, the amount will generally be between about 0.2% and about 2% by weight of the oil to be treated. Clays which may be employed include fullers earth, bentonite and acid activated montmorillonite.

The aldehyde and base, or clay, may be added to the oil to be distilled and mixed thoroughly with the oil prior to distillation or it may be added to the oil being distilled at some point in the lines leading to the furnace prior to fractionation or in some instances, it may be added to the oil at some point in the fractionation tower. Moreover, the aldehyde or aldehyde genitor may be added to the oil prior to the passage through the furnace and the caustic injected at some point in the distillation column, as for example at the trays just above the point at which the feed is introduced but below the tray from which the heaviest side stream is removed from the fractionating column. When clay is employed, it is generally added to the oil prior to passing the oil through the heating section of the distillation unit.

Although pretreatment of the oil to be distilled is not essential to the process of this invention it is observed that greater improvement in color stability of the resulting lubricating distillates and extract distillates is sometimes obtained when the aldehyde and caustic are mixed with the oil and permitted to remain in contact with the oil for a few minutes up to several days prior to distillation. This pretreatment or contacting may be at ordinary temperature or at elevated temperatures such as temperatures up to 325 F. or higher.

The following examples will serve to illustrate the invention.

Example I A San Joaquin Valley heavy crude oil having an API gravity at 60 F. of 15.1 and containing 1.0% by weight of water and 1.21% by weight of sulfur was dehydrated in order to simplify laboratory distillation by the following treatment. To 3500 ml. of the wet crude oil was added 1000 ml. of a light petroleum naphtha having a boiling range of approximately 140 F. to 210 F. and the mixture was refluxed, using a water trap in the reflux line, for about 4 hours. The dehydrated mixture was then distilled using a heated Vigreux column, approximately 1 inch in diameter and 28 inches high, up to an overhead vapor temperature of about 400 F. at 20 mm. of mercury pressure. The bottoms temperature was about 490 F. The distillate obtained in this manner was discarded and a lubricating oil fraction was then collected by continuing the distillation to an overhead temperature of 490 F. at 2-3 mm. of mercury pressure. The bottoms temperature at this time was about 570 F.

The lubricating oil fraction obtained in this manner had a boiling range of approximately 640 F. to 870 F. at atmospheric pressure as determined from a pressuretemperature alignment chart described by Beale and Docksey, Institute of Petroleum Technical Journal, volume 21, page 860 (1935), and is believed to contain lubricating oil from SAE up to and including SAE 40 grade. The initial color of this lubricating oil fraction was 3 A. S. T. M. This color is determined by the A. S. T. M. Union Colorimeter following the test method A. T. M. designation D15545T. After 4 weeks storage in the presence of air, the color was 4.5 and after 7 weeks storage the color was darker than 8 which is the darkest color which can be determined in the A. S. T. M. Colorimeter following the A. S. T. M. procedure without dilution.

The above operation was repeated except that following the removal of the lighter distillate fractions, the topped crude was agitated with about 0.5% by weight of paraformaldehyde and 0.13% by weight of 50% sodium hydroxide solution. After agitating for about 30 minutes, during which time the mixture was heated to 200 F., the material was distilled and a lubricating oil cut obtained under the same conditions of temperature and pressure as described in the previous operation. The original color of this lubricating oil fraction was slightly darker than 3 A. S. T. M. After 5 weeks storage in the presence of air, the color was 4.5 and after 10 weeks this fraction had an A. S. T. M. color of 5 The above operation was repeated except that paraformaldehyde was omitted and the reduced crude treated only with 0.13% by weight of 50% sodium hydroxide. In this case, the original color of the lubricating oil fraction was slightly less than 3 A. S. T. M. After 5 weeks storage in the presence of air, the color was nearly 6 A. S. T. M. and after 8 weeks, the color was 8 A. S. T. M.

Example 11 San Joaquin Valley crude oil, as described in Example I, was dehydrated following the procedure outlined in that example and then distilled in the apparatus described in Example I to a bottoms temperature of about 490 F. under pressure of about 200 mm. mercury. The solvent and the gasoline and part of the kerosene was removed by this procedure. The topped crude thus obtained was agitated and heated with about 0.13% of paraformaldehyde and about 0.13% by weight of 50% sodium hydroxide solution to a temperature of about 280 F. over a period of 1 hour. The mixture was then distilled to remove the remainder of the kerosene and diesel fuel and in this operation the final overhead vapor temperature reached 400 F. at 20 mm. of mercury pressure. The corresponding bottoms temperature was about 490 F. The distillate receiver was changed and the lubricating oil fraction collected from an initial overhead vapor temperature of 400 F. at 20 mm. to a final temperature of 490 F. at 2 mm. of mercury pressure. This lubricating oil distillate had an initial color of 3.5 A. S. T. M. which degraded to a 5 color after 9 weeks and a 7 color after 14 weeks storage in the presence of air.

Example III To 2000 ml. of San Joaquin Valley heavy crude was added 40 ml. of commercial 37% aqueous formaldehyde solution and 4 g. of 50% sodium hydroxide solution. The mixture was agitated at 140180 F. for about 2.5 hours. To this mixture was added 500 ml. of a light petroleum naphtha and the mixture refluxed for about 4 hours with a water trap in the reflux line and then subjected to distillation using the Vigreux column described in Example I. A lubricating oil fraction was collected under the same conditions of temperature and pressure described in Example I. The initial color of the lubricating oil fraction was 3 A. S. T. M. After 8 weeks the color was 5 A. S. T. M. and after 11 weeks of storage in the presence of air it was just slightly darker than 6 A. S. T. M.

For purposes of comparison and to show the effect of eliminating sodium hydroxide, the above procedure was carried out on a second portion of San Joaquin Valley heavy crude in the same manner except that sodium hydroxide solution was omitted. The color of the lubricating oil fraction produced was originally 3 A. S. T. M. and degraded to slightly darker than 5 after 7 weeks and 8 after 10 weeks of storage in the presence of air.

Example IV The first procedure of Example III was repeated except that the mixture of formaldehyde, caustic and crude oil was not heated prior to distillation but it was agitated at room temperature for 8hours on each of 5 successive days. In this instance, the original color of the lubricat- '5 ing oil fraction produced was 3.5 A. weeks of storage the color was 4 A. S. weeks it was only 4.5 A. S. T. M.

The procedure set forth in Example II was repeated except that 2% by weight of an active clay and 1% by weight of 37% aqueous formaldehyde were used in place of treating agents described in Example II. The lubricating oil distillate obtained originally had an A. S. T. M. color of 3.5. After 7 weeks the color was 6 A. S. T. M.

The above described procedure was repeated except that formaldehyde was omitted and the topped crude contacted only with active clay. The original color of the lubricating oil distillate produced was slightly darker than 3 A. S. T. M. but after 7 weeks the color was 8 A. S. T. M.

Although 2% by weight of an active clay was used in this example amounts ranging from 0.5 to 3 or :more of clay may be employed to give the desired results.

Example VI A lubricating oil extract fraction resulting from the commercial extraction with phenol of the lubricating distillate from San Joaquin Valley heavy crude was mixed with 2% of 37% formaldehyde and 0.8% of 50% sodium hydroxide solution for 8 hours at room temperature and then distilled using the Vigreux column described in Example I. This phenol extract was obtained from the entire SAE to SAE 60 lubricating oil distillate.

The mixture of extract, formaldehyde and caustic was distilled at 10 mm. of mercury pressure until approximately 30% by weight of the charge had been distilled, at which time the vapor temperature was 445 F. and the bottoms temperature 508 F. A second 30% fraction was then collected at a pressure of about 2 mm. of mercury. This fraction was completed at a vapor ternperature of 445 F. and a bottoms temperature of 518 F. A third fraction amounting to by weight was taken at a final vapor temperature of 518 F. and a bottoms temperature of 572 F.

Because of the low viscosity index of the extract fractions, cut 2 was extremely viscous and cut 3 was almost solid at room temperature. As a consequence ox gen diffusion into these samples took place very slowly and only the surface darkened. In order to follow the color degradation of the distilled product, it was necessary to prepare blends of the overhead material. The degradation in color of cut 1 was determined without blending, however, equal parts of cuts 1 and 2 were combined to give a 060% distillate fraction and a 0-80 distillate was prepared by combining 1 part of cut 3 with 1.5 parts of each of cuts 1 and 2. Each of the resulting blends was sufiiciently liquid to determine color degradation satisfactorily. Data regarding the color degradation of these fractions are presented in the table below.

For purposes of comparison a similar distillation and blending of distillate fractions was carried out on the phenol extract without the use of treating agents. Data regarding the degradation of color of the samples produced in this manner are also presented in the following table.

Color (A. S. 'I. M.), at indicated Percent time Treatment Overhead Initial 2Weeks 4weeks fiweeks 0-30 2 4 5 5 2% Formal! 0-60 4 4+ 4 5 4 s1- 1 0.8% l\aOH Solution [Hm 4. 5+ 5 5 6 0-30 2 6 8 None 0-60 3. 5+ 4. 5+ 6 8+ 6 Example VII Example II was repeated using 0.5% .by weight furfuraldehyde in place of the paraformaldehyde. The lubricating oil fraction collected in the temperature and pressure range indicated in Example II had an initial color of 3.5 A. S. T. M. which degraded to a 7 color after 10 weeks storage in the presence of air.

Example VIII Example II was repeated using 0.2% by weight of acetaldehyde in place of paraformaldehyde. The lubricating oil fraction produced in this treatment had a color stability substantially equivalent to that shown for the lubricating oil fraction produced in Example II.

Example .IX

Example II was repeated using calcium hydroxide in place of sodium hydroxide and the color stability of the lubricating oil distillate was substantially the same as shown in Example II.

By the term aldehyde substance as used herein is meant the low molecular weight aldehydes including formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde, and the formaldehyde genitors such as paraformaldehyde, trioxane and the like. These aldehyde substances all have the effect of improving the color stability of hydrocarbon distillate fractions boiling in the lubricating oil boiling range when added to hydrocarbon oils, especially mineral oils, prior to distillation and effecting the distillation in their presence and particularly when the distillation is effected in the presence of one of the aldehyde substances and an auxiliary agent as described herein above.

The foregoing description and examples are illustrative of the invention but are not to be taken as limiting the invention since many variations may be made without departing from the spirit and the scope of the following claims.

I claim:

1. A method of producing relatively color stable hydrocarbon fractions boiling in the lubricating oil boiling range which comprises distilling a hydrocarbon oil containing hydrocarbons boiling in said range in the presence of relatively small amounts of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and an auxiliary agent selected from the class consisting of the alkali and alkaline earth metal hydroxides and active clay.

2. A method of producing relatively color stable lubricating oil distillates which comprises distilling mineral oil containing lubricating oil fractions in the presence of relatively small amounts of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and an auxiliary agent selected from the class consisting of the alkali and alkaline earth metal hydroxides and active clay.

3. A method according to claim 2 in which said aldehyde substance is formaldehyde.

4. A method according to claim 2 in which said aldehyde substance is paraformaldehyde.

5. A method according to claim 2 in which said auxiliary agent is sodium hydroxide.

6. A method according to claim 2 in which said auxiliary agent is calcium hydroxide.

7. A method of producing relatively color stable lubricating oil solvent extract fractions which comprises distilling selective solvent extract in the presence of relatively small amounts of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and an auxiliary agent selected from the class consisting of the alkali and alkaline earth metal hydroxides and active clay.

8. A method of producing relatively color stable lubricating oil distillates which comprises distilling a mineral oil containing lubricating oil fractions in the presence of between about 0.1% and about 2% by weight of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and between about 0.2% and about 0.5% by weight of an alkali metal hydroxide.

9. A method of producing relatively color stable lubricating oil distillates which comprises distilling a mineral oil containing lubricating oil fractions in the presence of between about 0.1% and about 2% by weight of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and between about 0.02% and about 0.5% by weight of an alkaline earth metal hydroxide.

10. A method of producing relatively color stable lubricating oil distillates which comprises distilling a mineral oil containing lubricating oil fractions in the presence of between about 0.1% and about 2% by weight of an aldehyde substance selected from the class consisting of formaldehyde, acetaldehyde, propionaldehyde, furfuraldehyde and formaldehyde genitors and between about 0.5 and about 3% of an active clay.

11. A'method according to claim 2 in which said mineral oil containing lubricating oil fractions is a reduced crude oil.

12. A method according to claim 2 in which said mineral oil containing lubricating oil fractions is a lubricating oil distillate fraction.

13. A method according to claim 2 in which said mixture of aldehyde substance, auxiliary treating agent and mineral oil is agitated at elevated temperatures prior to the distillation step.

References Cited in the file of this patent UNITED STATES PATENTS 2,404,253 Scarth July 16, 1946 2,567,174 Arundale et al. Sept. 11, 1951 2,616,832 Browder Nov. 4, 1952 2,675,305 Rogers et al. Apr. 13, 1954 

1. A METHOD OF PRODUCING RELATIVELY COLOR STABLE HYDROCARBON FRACTIONS BOILING IN THE LUBRICATING OIL BOILING RANGE WHICH COMPRISES DISTILLING A HYDROCARBON OIL CONTAINING HYDROCARBONS BOILING IN SAID RANGE IN THE PRESENCE OF RELATIVELY SMALL AMOUNTS OF AN ALDEHYDE SUBSTANCE SELECTED FROM THE CLASS CONSISTING OF FORMALDEHYDE, ACETALDEHYDE, PROPIONALDEHYDE, FURFURALDESHYDE AND FORMALDEHYDE GENITORS AND AN AUXILIARY AGENT SELECTED FROM THE CLASS CONSISTING OF THE ALKALI AND ALKALINE EARTH METAL HYDROXIDES AND ACTIVE CLAY. 